Heated vascular occlusion coil deployment system

ABSTRACT

An embolic coil deployment system for placing a coil at a preselected site within a vessel of the human body. The deployment system includes a heating element at the distal end of a delivery member and a heat responsive coupling for holding the coil during positioning of the coil and activation means for releasing the coil at a desired position within the vessel.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a medical device for placing anembolic coil at a preselected location within a vessel of the humanbody, and more particularly, relates to a flexible delivery memberhaving a heating element and a heat responsive coupling member at thedistal tip of the delivery member for holding the embolic coil in orderto transport the coil to a desired position within the vessel andrelease the embolic coil at that position.

[0003] 2. Description of the Prior Art

[0004] For many years flexible catheters have been used to place variousdevices within the vessels of the human body. Such devices includedilatation balloons, radiopaque fluids, liquid medications and varioustypes of occlusion devices such as balloons and embolic coils. Examplesof such catheter devices are disclosed in U.S. Pat. No. 5,108,407,entitled “Method And Apparatus For Placement Of An Embolic Coil”; U.S.Pat. No. 5,122,136, entitled, “Endovascular Electrolytically DetachableGuidewire Tip For The Electroformation Of Thrombus In Arteries, Veins,Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” Thesepatents disclose devices for delivering embolic coils to preselectedpositions within vessel of the human body in order to treat aneurysms,or alternatively, to occlude the blood vessel at the particularlocation.

[0005] Coils which are placed in vessels may take the form of helicallywound coils, or alternatively, may be random wound coils, coils woundwithin other coils or many other such configurations. Examples ofvarious coil configurations are disclosed in U.S. Pat. No. 5,334,210,entitled, “Vascular Occlusion Assembly; U.S. Pat. No. 5,382,259,entitled, “Vasoocclusion Coil With Attached Tubular Woven Or BraidedFibrous Coverings.” Embolic coils are generally formed of radiopaquemetallic materials, such as platinum, gold, tungsten, or alloys of thesemetals. Often times, several coils are placed at a given location inorder to occlude the flow of blood through the vessel by promotingthrombus formation at the particular location.

[0006] In the past, embolic coils have been placed within the distal endof the catheter. When the distal end of the catheter is properlypositioned the coil may then be pushed out of the end of the catheterwith, for example, a guidewire to release the coil at the desiredlocation. This procedure of placement of the embolic coil is conductedunder fluoroscopic visualization such that the movement of the coilthrough the vasculature of the body may be monitored and the coil may beplaced at the desired location. With these placements systems there isvery little control over the exact placement of the coil since the coilmay be ejected to a position some distance beyond the end of thecatheter.

[0007] Numerous procedures have been developed to enable more accuratepositioning of coils within a vessel. Still another such procedureinvolves the use of a glue, or solder, for attaching the embolic coil toa guidewire which, is in turn, placed within a flexible catheter forpositioning the coil within the vessel at a preselected position. Oncethe coil is at the desired position, the coil is restrained by thecatheter and the guidewire is pulled from the proximal end of thecatheter to thereby cause the coil to become detached from the guidewireand released from the catheter system. Such a coil positioning system isdisclosed in U.S. Pat. No. 5,263,964, entitled, “Coaxial TractionDetachment Apparatus And Method.”

[0008] Another coil positioning system utilizes a catheter having asocket at the distal end of the catheter for retaining a ball which isbonded to the proximal end of the coil. The ball, which is larger indiameter than the outside diameter of the coil, is placed in a socketwithin the lumen at the distal end of the catheter and the catheter isthen moved into a vessel in order to place the coil at a desiredposition. Once the position is reached, a pusher wire with a piston atthe end thereof is pushed distally from the proximal end of the catheterto thereby push the ball out of the socket in order to release the coilat the desired position. Such a system is disclosed in U.S. Pat. No.5,350,397, entitled, “Axially Detachable Embolic Coil Assembly.” Oneproblem with this type of coil placement system which utilizes a pusherwire which extends through the entire length of the catheter and whichis sufficiently stiff to push an attachment ball out of engagement withthe socket at the distal end of the catheter is that the pusher wireinherently causes the catheter to be very stiff with the result that itis very difficult to guide the catheter through the vasculature of thebody.

[0009] Another method for placing an embolic coil is that of utilizing aheat releasable adhesive bond for retaining the coil at the distal endof the catheter. One such system uses laser energy which is transmittedthrough a fiber optic cable in order to apply heat to the adhesive bondin order to release the coil from the end of the catheter. Such a methodis disclosed in U.S. Pat. No. 5,108,407, entitled, “Method And ApparatusFor Placement Of An Embolic Coil.” Such a system also suffers from theproblem of having a separate, relatively stiff element which extendsthroughout the length of the catheter with resulting stiffness of thecatheter.

[0010] Still another method for placing an embolic coil is disclosed inco-pending U.S. patent application Ser. No. 09/177,848, entitled,“Embolic Coil Hydraulic Deployment System,” filed on Oct. 22, 1998 andassigned to the same assignee as the present patent application. Thispatent application discloses the use of fluid pressure which is appliedto the distal tip of the catheter for expanding the lumen of thecatheter in order to release the embolic coil.

SUMMARY OF THE INVENTION

[0011] The present invention is directed toward a vascular occlusioncoil deployment system for use in placing an embolic coil at apreselected site within a vessel which includes an elongated flexiblepositioning member having a lumen extending therethrough. An elongatedflexible delivery member having a lumen extending therethrough isslidably positioned within the lumen of the positioning member. Aheating element is affixed to the distal end of the delivery member anda heat responsive coupling member adhesively bonds the embolic coil tothe heating element. The heating element is adapted to be coupled to asource of energy through an energy transmission conductor which extendsthrough the lumen in the delivery member. The heat responsive couplingmember, bonding the heating element to the embolic coil, exhibits thecharacteristic of softening and yielding upon being heated. When energyis applied through the conductor to the heating element, the heatingelement causes the heat responsive coupling member to yield to therebyrelease the embolic coil at the preselected site.

[0012] In accordance with another aspect of the present invention, theheating element takes the form of resistive heating coil. At least aportion of this resistive heating coil is bonded to the interior of theheat responsive coupling member to thereby directly apply heat to thecoupling when the heating coil is supplied with electrical energy.

[0013] In accordance with still another aspect of the present invention,the vascular occlusion coil deployment system for use in placing anembolic coil at a preselected site within a vessel includes an elongatedflexible positioning member having a lumen extending therethrough. Anelongated flexible delivery member is slidably positioned within thelumen of the positioning member. A heating element is affixed to thedistal end of the delivery member and a heat responsive coupling memberadhesively bonds the embolic coil to the heating element. The heatingelement is adapted to be coupled to a source of energy through an energytransmission conductor. The energy transmission conductor extends fromthe proximal end to the distal end of the delivery member through thelumen of the positioning member and is coupled to the heating element.The heat responsive coupling member, bonding the heating element to theembolic coil, exhibits the characteristic of softening and yielding uponbeing heated. When energy is applied through the conductor to theheating element, the heating element causes the heat responsive couplingmember to yield to thereby release the embolic coil at the preselectedsite.

[0014] In accordance with still another aspect of the present invention,the energy transmission conductor takes the form of two electricalconductors which extend through the lumen of the delivery member and areconnected to the resistive heating coil for applying electrical energyto the coil to thereby cause the coil to become heated.

[0015] In accordance with still another aspect of the present invention,the heating element is disposed within a lumen of the embolic coil. Theheat responsive coupling member bonds the embolic coil to the heatingelement. When the heating element is energized the heat responsivecoupling member heats. Upon heating the heat responsive coupling membersoftens thereby reducing its yield strength. This allows the heatingelement to be retracted into the positioning member breaking the heatresponsive coupling member to release the coil.

[0016] In accordance with still another aspect of the present invention,the heat responsive coupling member is comprised of a hot melt adhesive.Other suitable materials include low melting temperature metals andmetal alloys such as solder. Other suitable materials are those whoseyield strength decreases by at least 50 percent when heated to about 65degrees Celsius.

[0017] These aspects of the invention and the advantages thereof will bemore clearly understated from the following description and drawings ofa preferred embodiment of the present invention:

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is an enlarged, partially sectioned view of the vascularocclusion coil deployment system of the present invention;

[0019]FIG. 2 is an enlarged partially sectioned view showing the coildeployment system prior to placement within a catheter;

[0020]FIGS. 3 through 5 are enlarged partially sectioned viewsillustrating the sequential steps of positioning the vascular coilwithin a vessel and releasing the coil at a preselected site.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0021]FIG. 1 generally illustrates a preferred embodiment of a vascularocclusion coil deployment system 10 of the present invention which iscomprised of an elongated flexible catheter 12 which is utilized toposition a coil deployment mechanism 14. A Luer connector 16 isconnected to the proximal end of the catheter 12 and the coil deploymentmechanism 14 is connected to a power supply 18 for applying energy tothe coil deployment mechanism 14.

[0022]FIG. 2 illustrates in more detail the construction of the coildeployment mechanism 14. More particularly, the deployment mechanism 14includes an elongated positioning member 22 which is approximately thesame length as the outer catheter 12 and which is slidably received bythe catheter 12. Positioning member 22 has a lumen extending from itsproximal end to its distal end. Coil deployment mechanism 14 alsoincludes a tubular, delivery member 24 which is slidably positionedwithin the lumen of positioning member 22. Located at the distal end ofthe delivery member 24 is a heating element 26. The heating element 26is bonded to the embolic coil 20 by a heat responsive coupling member30.

[0023] The heat responsive coupling member 30 may take the form of anybiocompatible adhesive which, upon being heated, softens so that it maybe stretched. Preferably, this heat responsive coupling member 30 iscomprised of a hot melt adhesive, such as, for example, a hot meltadhesive manufactured by Minnesota Mining and Manufacturing sold underthe name Jet Melt, Catalog No. 3783TC. The temperature required tosoften this material is on the order of 63 degrees centigrade.

[0024] Also, as illustrated in FIG. 2, the heating element 26 which ispreferably a resistively heated coil is coupled to a pair of energytransmission conductors 28, 29. Preferably the energy transmissionconductors 28, 29 are electrical conductors also coupled to power supply18. Upon application of an electrical current to the pair of conductors28, 29 the heating element 26 begins to heat to thereby cause the heatresponsive coupling member 30 to increase in temperature. As the heatresponsive coupling member 30 becomes warm it softens and has a loweryield strength, thus, breaking when the delivery member 24 is retractedto release the embolic coil 20.

[0025] More particularly, and as illustrated in FIGS. 3 through 6, thevascular occlusion coil deployment system 10 is inserted into a bloodvessel 40 and is moved to a position within the blood vessel 40 to aposition where it is desirable to place the embolic coil 20. When thecatheter 12 has been positioned at a location slightly proximal of thepreselected site for placement of the embolic coil (FIG. 4), the coildeployment mechanism 14 is pushed out of the distal end of the catheter12 and electrical energy is then applied to the heating element 26 tothereby soften the heat responsive coupling member 30. Once the heatresponsive coupling member 30 softens, the delivery member 24 isretracted, thus disengaging the heating element 26 from embolic coil 20breaking the adhesive bond of heat responsive coupling member 30. As thedelivery member 24 is retracted, there is no longer engagement betweenthe heating element 26 and the embolic coil 20 and the coil is released.

[0026] Finally, and as illustrated in FIG. 6, the coil deploymentmechanism 14 is withdrawn back into the catheter 12 and the embolic coil20 remains in its deployed position.

[0027] With the vascular occlusion coil deployment system of the presentinvention it is possible to place an embolic coil very precisely at adesired location within a vessel. Once the coil has been placed in apreselected location by catheter, the deployment mechanism may beactivated by applying energy to a coil release mechanism to therebycause the coil to be released and deposited at a desired location.

[0028] As is apparent, there are numerous modifications of the preferredembodiment described above which will become readily apparent to oneskilled in the art, such as many variations and modifications of thedeployment system including many different variations of the heatingelement, many variations of energy sources for heating the adhesive suchas optical, radiofrequency, and acoustical, many variations of energytransmission conductors such as optical fiber, and many variations ofheat softening adhesives.

[0029] These modifications would be apparent to those having ordinaryskill in the art to which this invention relates and are intended to bewithin the scope of the claims which follow.

That which is claimed is:
 1. A vascular occlusion coil deployment systemfor use in placing a coil at a preselected site within a vesselcomprising: an elongated flexible positioning member having a lumenextending therethrough and having proximal and distal ends; an emboliccoil; an elongated flexible delivery member having a lumen extendingtherethrough and being positioned within the lumen of the positioningmember and having proximal and distal ends; a heating element mounted onthe distal end of the delivery member; an energy transmission conductorextending through the lumen of the delivery member and extending fromthe proximal end to the distal end of the delivery member, said energytransmission conductor being coupled to said heating element; and, aheat responsive coupling member adhesively bonded to both the heatingelement and to the embolic coil, said heat responsive coupling memberexhibits the characteristic of, upon being heated, releasing itsadhesive bond whereby upon applying energy through the energytransmission conductor to the heating element, the heating elementcauses the heat responsive coupling member to release the embolic coilat the preselected site.
 2. A vascular occlusion coil deployment systemas defined in claim 1 , wherein said heating element is an electricallyheated coil.
 3. A vascular occlusion coil deployment system as definedin claim 2 , wherein said heat responsive coupling member is formed of asolid material, wherein the yield strength is reduced at least 50percent when heated to about 65 degrees Celsius, between said heatingelement and said embolic coil.
 4. A vascular occlusion coil deploymentsystem as defined in claim 3 , wherein said solid material is formed ofa polymer.
 5. A vascular occlusion coil deployment system as defined inclaim 3 , wherein said solid material is formed of a metal alloy.
 6. Avascular occlusion coil deployment system as defined in claim 1 ,wherein said heat responsive coupling member between said heatingelement and said embolic coil occurs within a lumen of said emboliccoil.
 7. A vascular occlusion coil deployment system as defined in claim1 , wherein said energy is electrical energy.
 8. A vascular occlusioncoil deployment system for use in placing coil at a preselected sitewithin a vessel comprising: an elongated flexible positioning memberhaving a lumen extending therethrough and having proximal and distalends; an embolic coil; an elongated flexible delivery member beingpositioned within the lumen of the positioning member and havingproximal and distal ends; a heating element mounted on the distal end ofthe delivery member; an energy transmission conductor extending throughthe lumen of the positioning member, said energy transmission conductorbeing coupled to said heating element; and, a heat responsive couplingmember bonded to both the heating element and to the embolic coil, saidheat responsive coupling member exhibits the characteristic of, uponbeing heated, having a reduced adhesive force whereby upon applyingenergy through the energy transmission conductor to the heating element,the heating element causes the heat responsive coupling member torelease the embolic coil at the preselected site.
 9. A vascularocclusion coil deployment system as defined in claim 8 , wherein saidheating element is an electrically heated coil.
 10. A vascular occlusioncoil deployment system as defined in claim 9 , wherein said heatresponsive coupling member is formed of a solid material, wherein theyield strength is reduced at least 50 percent when heated to about 65degrees Celsius, between said heating element and said embolic coil. 11.A vascular occlusion coil deployment system as defined in claim 10 ,wherein said solid material is formed of a polymer.
 12. A vascularocclusion coil deployment system as defined in claim 10 , wherein saidsolid material is formed of a metal alloy.
 13. A vascular occlusion coildeployment system as defined in claim 8 , wherein said heat responsivecoupling member between said heating element and said embolic coiloccurs within a lumen of said embolic coil.
 14. A vascular occlusioncoil deployment system as defined in claim 8 , wherein said energy iselectrical energy.
 15. A vascular occlusion coil deployment system foruse in placing a coil at a preselected site within a vessel comprising:an elongated flexible positioning member having a lumen extendingtherethrough and having proximal and distal ends; an embolic coil; anelongated flexible delivery member being slidably positioned within thelumen of the positioning member and having proximal and distal ends; aheating element mounted on the distal end of the delivery member; anenergy transmission conductor extending through the lumen of thepositioning member, said energy transmission conductor being coupled tosaid heating element; and, a heat responsive coupling member bonded toboth the heating element and to the embolic coil, said heat responsivecoupling member exhibits the characteristic of, upon being heated,softening thereby reducing its yield strength whereby upon applyingenergy through the energy transmission conductor to the heating elementthe heating element causes the heat responsive coupling member to breakthereby releasing the embolic coil at the pre-selected site.
 16. Avascular occlusion coil deployment system as defined in claim 15 ,wherein said heating element is an electrically heated coil.
 17. Avascular occlusion coil deployment system as defined in claim 16 ,wherein said heat responsive coupling member is formed of a solidmaterial, wherein the yield strength is reduced at least 50 percent whenheated to about 65 degrees Celsius, between said heating element andsaid embolic coil.
 18. A vascular occlusion coil deployment system asdefined in claim 17 , wherein said solid material ifs formed of apolymer.
 19. A vascular occlusion coil deployment system as defined inclaim 17 , wherein said solid material is formed of a metal alloy.
 20. Avascular occlusion coil deployment system as defined in claim 15 ,wherein said heat responsive coupling member between said heatingelement and said embolic coil occurs within a lumen of said emboliccoil.
 21. A vascular occlusion coil deployment system as defined inclaim 15 , wherein said energy is electrical energy.